First WGIII meeting

Work group 3 meetings were attended by 21 participants

I. Clarification of basic concepts

A. STRESS: Input from Armando Lenz: plant physiological concepts of „stress“ concepts on plants. Stress is a destructive form of limitation, can be abrupt or gradual.

Changes in site conditions may also be abrupt (e.g. flooding with nutrient input) or gradual (e.g. atmospheric N-input or acidification).

Physiological processes in plant can be transient (e.g. photosynthesis) or cumulative (growth). How to define thresholds for stress? Suggestion: Concept of „fitness“ (see graph below).

B. Genetics: Georg v. Wuehlisch reported about results from provenance trials (COST Aktion E52). At present, statistical effects of genes are week and genetically not well determined. Concerning the research gaps on genetics relevant for our cost action, the following suggestions are made:

for WG1: include a button ‚autochthonous‘ versus ‚allochthonous‘ tree populations in the data base

if ‚allochthonous‘ holds true for samples collected, try to find out provenance or source of origin (if managed forest)

Study of stress effects on trees at the source of the provenances vs. Plantation plots

Application of genetic markers (development in forthcoming ca. 2-3 years for several species) for proper characterization of genotypes

Calculation of genetic distances in trees of a population

Studies of adaptive capacity of genotypes

Adaptation potential of certain traits in different genotypes to environmental stress

General suggestion: include other woody plants (shrubs) into the perspective (WG1)

Additional aspects to be mentioned are long-term environmental changes (e.g. climate warming, atmospheric CO2-increase, remote fertilization) that may alter plant responses to short-term extreme events. Beside the individual stress factors, combinations of several factors have to be taken into account.

III. Next steps until Napels

How do we define “extreme events” in the context of climatic differences over Europe (may be including other regions where data are collected)? E.g. what is drought in context of boreal or Mediterranean climate? Do we see this from event frequencies (100 year event, 1000-year event), from statistical thresholds or from the effects visible in the plants? For clarification, consultancy of colleagues (e.g. van der Schrier, local climatologists)

2. Organisation of review papers to summarize the state of the art and to identify research gaps